Composite ropes, cords and the like



March 1 1961 E. coca] 2,974,559

COMPOSITE ROPES, CORDS AND THE LIKE Filed July 25, 1958 POLYPROPYLENE SHEATH JUTE CORE INVENTOR E TTORE COGG/ Bywmgmm,

ATTORNEY5 the like.

"ttes 2,974,559 "eoMPosITn Roms, coups AND LIKE Ettore Coggi, .Milan, i Italy, assignor t Montecatini- Societa Generale per llndustria Miner-aria e Chimica, Milan, Italy Filed Jul 25, 1958, Ser. No. 750,885 M "Claims priority, application Italy July 29, 15957 13 Claims. (CI. 87- 1) This invention relates to a new article of manufacture for use as a rope, cord or the like, and which "comprises natural and synthetic fibers. More particularly, the invention 'relates to a rope consisting essentially 'of a core made from jute fibers and a sheath yarn of 'a" high molecular weight, substantially isotactic polypropylene.

Ropes made of jute fibers have good mechanicalproperties. However, the use of jute for rope-making is re- Patented Mar. 14, 1961 able orifices and twisting the resulting filaments together to form a yarn.

The yarn can be subjected to a thermal stabilizing treatment but is preferably plaited onto the jute core without stricted by the inability of the jute fibers to resist chemical agentssuch as the salts contained in sea water, and

Moisture readily causes the degrading hydrolysis of the cellulose of the jute. Also, the bacterial flora developed by microorganisms on'the cellulose rapida 1y destroy it and weaken the rope.

Ithas been attempted to increase the utility of jute ropes by coating or impregnating them with extraneous insulating and protecting materials. Up to the present time, only poor results have been obtained by resorting to such expedients. Either the protection aiiorded to the jute was inadequate, or the coating or impregnating material increased the cost of the rope prohibitively.

A primary object of :this invention is to provide new ropes which are inherently resistant to chemicals, including the salts present in sea water.

We find that it is possible to obtain ropes containing jute fibers but which have excellent resistance to moisture and atmospheric and chemical agents, by plaiting onto a jute core a yarn of substantially isotactic polypropylene, and then subjecting the composite structure to a thermal treatment which causes the polypropylene'sheath to shrink and adhere tenaciously to the jute core.

The substantially isotactic polypropylene which we use for making the yarn which constitutes the sheath of our ropes is a polypropylene substantially made up of isotactic macromolecules, i.e., macromolecules having substantially isotactic structure and as diselosedrecently by G. Natta and his co-workers (eg, in two papers entitled, respectively, A New Class of Alpha- Olefin Polymers Having Exceptional Uniformity of Structure and The Crystalline Structure of a New Type of Polypropylene which were presented at an open meeting of Accademia Nazionale Dei Lincei on December 1d, 1954, and published in the Proceedings of the Accademia on January 29, 1955).

As Natta et al. have disclosed, isotactic polypropylene is a polymer which consists of isotactic macromolecules, i.e., linear, regular head-to-tail macromolecules having substantially no branches longer than the CH group, having substantially the Natta isotactic structure, and which are non-extractable with boiling n-heptane.

The isotactic structure of the polypropylene macromolecule is characterized intha-t substantially allof the tertiary asymmetric carbon atoms of adjacent mono merit: units have the same stearic configuration and, arbitrarily assuming the macromolecule tobe fully extended in a plane, substantially all of the R(CH (in the case of polypropylene) substituents on the tertiary carbon atoms are on one side (eg. above) and the H atoms are on the a prior heat-treatment so that maximum shrinkage thereof occurs when the composite structure is heated after the plaiting step. i

. The temperature at which the composite structure is heated to effect shrinkage of the sheath depends on whether or not the substantially isotactic, polypropylene yarn has been heated prior to being plaited on the' core.

Preferably, the sheath is formed by a yarn of the substantially isotactic and. highly crystalline polypropylene,

because such polymers have a high elastic modulus and a high compressive effect on the jute core. The compressive action exerted by the yarn of substantially isotactic polypropylene is such that the twisting which is generally used in making jute ropes can be reduced or even eliminated, and the core can consist of a bundle of parallel, untwisted jute filaments with a consequent considerable saving in the time required to make the rope and in the production costs.

Surprisingly, the tensile strength of our ropes is increased by the polypropylene sheath .to an extent such that the tensile strength of the rope isabout 50% greater than the sum of the tensile strengths of the jute core and the polypropylene sheath.

The characteristics of the rope can be further improved by treating the rope with solvents which have a swelling efit'ect on the polypropylene sheath, before the rope is heated to shrink the sheath.

In fact, we find that treatment of the polypropylene sheath with such solvents and swelling thereof results in a more perfect sealing of the interstices between'the filaments of the sheath yarnand between the folds of the plait, and the more perfect sealing results in greater con tinuity of the sheath. The solvent treatment also results in dissolution of linear, regular head-to-tail atactic (amorphous) portions of-the polypropylene and the dissolution has theeffect of increasing the adherence of sheath is plaited thereon, or to spread such a solution on the finished rope.

Solutions of trom 5% to 20% of the atactic polypropylene or stereoblockpolypropylene (that is a polypropylene containing in the macromolecule both isotactic chain'portions and linear regularhead-to-tail ataotic, amorphous, non-crystallizable chain portions) can be used, preferably at a temperature above room tempera- The cords and ropes of this invention have many advantages as substitutes for jute ropes. In addition to the usual uses of such ropes, the present products can be used as driving elements on wire guide pulleys for various machines, where a high friction coefficient on steel is necessary to avoid slipping.

The coeflicient is calculated from the formula where P and P indicate, respectively, the tension on the yarn, before and after a steel cylinder on which the yarn to be examined is wound up with turns forming angles of radiants. These tensions are measured by means of a weight bridge system.

As between the polypropylene yarn and a steel pulley, the coefiicient determined as described is 0.30 whereas it is only 0.25 between jute and steel. Such coefficient is therefore 20% higher for the polypropylene, which results in a remarkable improvement in the driving efliciency when the present composite jute cord and polypropylene sheath ropes are used.

The following example, which is by no means limiting, is illustrative of the invention.

Example A core is made from 3 jute yarns of 450 meter/kg, the yarns being assembled in parallel, without twisting together.

A sheath consisting of a 7200 meter/kg. double yarn of substantially isotactic polypropylene is applied over the jute core by means of a plaiting machine. This yarn was previously subjected to a thermal treatment in order to remove the hairiness. The composite rope thus ob tained is then immersed in a suspension of carbon black in boiling trichloroethylene and, after removal from the suspension, is placed in an oven at about 160 C. and kept in the oven for 4 minutes.

Tensile strength tests carried out on the jute yarns and on the final composite ropes using a Schoppers dynamorneter (capacity 200 kg., tension rate 10 m./min., distance between the grips 5 OIIL, conditioning at 65% relatively humidity and 20 C.) give the following results Kg. Ultimate tensile strength of the 3 core jute yarns 90 Ultimate tensile strength of the polypropylene sheath Ultimate tensile strength of the rope consisting of the jute core and polypropylene sheath prior to the solvent and heat treatment 103 Ultimate tensile strength of the rope after the solvent and heat treatments About 150 As will be apparent, the composite ropes of the invention have a very high tensile strength. These ropes are also resistant to molds and bacteria as well as to alkalis and acids, even at high temperatures. They can be used for all purposes, including use as marine ropes, for which a strong, durable rope exposed in use to chemical attack is required.

As Natta et al. have shown, the isotactic polypropylene macromolecules are produced when propylene is polymerized in the presence of certain catalysts prepared from heavy metal-halides such as titanium halides and organometallic compounds like triethyl aluminum. If the catalyst is obtained by reduction of a high valency halide of the heavy metal, e.g., TiCl, with the organometallic compound, the crude polymerizate comprises the isotactic (crystallizable) macromolecules in mixture with a substantial amount of linear, regular head-to-tail atactic (amorphous, non-crystallizable) macromolecules. The isotactic polypropylene made of isotactic macromolecules remains as residue when the crude polymerizate is extracted with boiling n-heptane. On the other hand, as Natta et al. have also shown, if the catalyst is prepared by starting with a solid, crystalline low valency halide of the heavy metal, e.g. violet crystalline TiCl and mixing the crystalline halide with triethyl aluminum, the polymerization of the propylene is oriented to the production of isotactic macromolecules and the crude polymerizate consists prevailingly of substantially isotactic macromolecules.

By substantially isotactic polypropylene as used herein is meant a polypropylene being rather completely made up of the macromolecules having substantially isotactic structure as defined.

Since in practicing the invention some changes and variations may be made in details, as for instance in the number and type of the jute yarns making up the core and in the number of fibers twisted together to form the polypropylene sheath, without departing from the spirit thereof, it is intended to include in the scope of the appended claims all such modifications as may be apparent to those skilled in the art.

What is claimed is:

1. As a new article of manufacture, a composite fibrous structure consisting essentially of a core made of jute fibers and a yarn of a substantially isotactic polypropylene having a crystallinity of at least 70%, plaited on the core and forming an adhering, continuous sheath on the core.

2. As a new article of manufacture, a composite rope consisting essentially of a core made of jute fibers and a yarn of a substantially isotactic polypropylene having a crystallinity of at least 70% plaited on the core, the interstices between the turns of the plaited yarn being sealed as a result of a heat-softening of said plaited yarn, and said yarn forming a firmly adhering, continuous sheath on the core.

3. As a new article of manufacture, a composite rope consisting essentially of a core made of jute fibers irn pregnated with a linear, regular head-to-tail atactic polypropylene, and a yarn of a substantially isotactic polypropylene having a crystallinity of at least 70% plaited on the core and forming an adhering, continuous sheath on the core.

4. As a new article of manufacture, a composite rope consisting essentially of a core made of jute fibers impregnated with a stereoblock polymer of propylene, and a yarn of a substantially isotactic polypropylene plaited on the core and forming an altering, continuous sheath on the core.

5. As a new article of manufacture, a composite rope consisting essential of a core made of jute yarns and a yarn of a substantially isotactic polypropylene having a crystallinity of at least 70% plaited on the core, said yarn being coated with a linear, regular head-to-tail atactic polypropylene.

6. As a new article of manufacture, a composite rope consisting essentially of a core made of jute fibers and a yarn of a substantially isotactic polypropylene having a crystallinity of at least 70% plaited on the core, said rope having a friction coefiicient on steel which is about 20% higher than the friction coefficient on steel of a rope made of jute fibers only.

7. The method of making composite fibrous structures which comprises plaiting a sheath yarn of a substantially isotactic polypropylene having a crystallinity of at least 70% but containing some linear regular head-to-tail atactic polypropylene onto a core made of jute fibers, and treating the composite structure thus obtained with a solvent for the atactic polypropylene at a temperature not higher than C.

8. The method for making a composite fibrous structure which comprises plaiting a sheath yarn of a substantially isotactic polypropylene having a crystallinity of at least 70% but containing some linear, regular headto-tail atactic polypropylene onto a core made of jute fibers, treating the composite structure thus obtained with a solvent for the atactic polypropylene, and then heating the structure to a temperature between 120 C. and 170 C.

9. The method for making a composite fibrous structure which comprises plaiting a sheath yarn of a substantially isotactic polypropylene having a crystallinity of at least 70% onto a core made of jute fibers, treating the composite structure thus obtained with a solution of linear, regular head-to-tail atactic polypropylene at a temperature not higher than about 110 C., and then heating the structure to a temperature between 120 C. and 170 C.

10. The method for making a composite fibrous structure which comprises plaiting a sheath yarn of a substantially isotactic polypropylene having a crystallinity of at least 70% onto a core made of jute fibers, treating the composite structure thus obtained with a solution of a stereoblock polymer of propylene at a temperature not higher than about 110 C., and then heating the structure to a temperature between 120 C. and 170 C.

11. The method for making a composite fibrous structure which comprises plaiting a sheath yarn of a substantially isotactic polypropylene having a crystallinity of at least 70% onto a core made of jute fibers, treating the composite structure thus obtained with a solution of linear, regular head-toatailj atactic polypropylene in trichlorethylene at a temperature not higher than about 110 C., and then heating the structure to a temperature between 120 C. and 170 C.

12. The method for making a composite fibrous structure which comprises plaiting a sheath yarn of a substantially isotactic polypropylene having a crystallinity of at least onto a core made of jute fibers, treating the composite structure thus obtained with a solution of a stereoblock polymer of propylene in trichlorethylene at a temperature not higher than about C., and then heating the structure to a temperature between C. and C.

13. The method for making a composite fibrous structure which comprises plaiting a sheath yarn of a substantially isotactic polypropylene having a crystallinity of at :least 70% onto a core made of jute fibers, treating the composite structure thus obtained with a solution of a stereoblock polymer of propylene in a solvent selected from the group consisting of aliphatic, aromatic and cycloparafiinic hydrocarbons having a boiling point below 200 C., at a temperature not higher than about 110 C.

References Cited in the file of this patent France Feb. 5, 

1. AS NEW ARTICLE OF MANUFACTURE, A COMPOSITE FIBROUS STRUCTURE CONSISTING ESSENTIALLY OF A CORE MADE OF JUTE FIBERS AND A YARN OF A SUBSTANTIALLY ISOTACTIC POLYPROPYLENE HAVING A CRYSTALLINTY OF AT LEAST 70%, PLATED ON THE CORE AND FORMING AN ADHERING CONTINUOUS SHEATH ON THE CORE. 